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Nuclear IKKbeta is an adaptor protein for IkappaBalpha ubiquitination and degradation in UV-induced NF-kappaB

Yoshihiro Tsuchiya1, Tomoichiro Asano, Keiko Nakayama

  • 1Laboratory of Biomedical Chemistry, Department of Molecular Medical Science, Graduate School of Biomedical Science, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553, Japan.

Molecular Cell
|August 28, 2010
PubMed

Proinflammatory cytokines activate NF-kappaB using the IkappaB kinase (IKK) complex that phosphorylates inhibitory proteins (IkappaBs) at N-terminal sites resulting in their ubiquitination and degradation in the cytoplasm. Although ultraviolet (UV) irradiation does not lead to IKK activity, it activates NF-kappaB by an unknown mechanism through IkappaBalpha degradation without N-terminal phosphorylation. Here, we describe an adaptor function of nuclear IKKbeta in UV-induced IkappaBalpha degradation. UV irradiation induces the nuclear translocation of IkappaBalpha and association with IKKbeta, which constitutively interacts with beta-TrCP through heterogeneous ribonucleoprotein-U (hnRNP-U) leading to IkappaBalpha ubiquitination and degradation. Furthermore, casein kinase 2 (CK2) and p38 associate with IKKbeta and promote IkappaBalpha degradation by phosphorylation at C-terminal sites. Thus, nuclear IKKbeta acts as an adaptor protein for IkappaBalpha degradation in UV-induced NF-kappaB activation. NF-kappaB activated by the nuclear IKKbeta adaptor protein suppresses anti-apoptotic gene expression and promotes UV-induced cell death.

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